Hydrogen adsorption and desorption on SiGe investigated by in situ surface infrared spectroscopy

The hydrogen adsorption and desorption processes in SiGe films epitaxially grown on Si(100), were investigated using in situ infrared absorption spectroscopy (IRAS) in the multiple internal reflection geometry. We have measured Si-H and Ge-H stretching vibration spectra to examine how the distribution of hydride species (SiH_x and GeH_x) changes while exposed to atomic hydrogen at room temperature, and also to follow chemical changes of the H-exposed SiGe surface caused by thermal annealing. IRAS data demonstrate that the SiGe surface that is exposed to hydrogen after annealing at approximately 700°, is dominantly covered with Ge hydrides. When the surface is annealed up to approximately 400° the Ge-H vibration peak vanished completely, and instead, the Si-H vibration peak increased its intensity. We suggest that upon thermal annealing the hydrogen adatoms migrate from Ge sites to Si sites and the Ge atoms on the outermost layer are replaced with the inner Si atoms.